Interspinous spacer

ABSTRACT

A novel implantable spacer for placement between adjacent spinous processes in a spinal motion segment is provided. The spacer includes a body defining a longitudinal passageway. A first arm and a second arm are connected to the body. Each arm has a pair of extensions and a saddle defining a U-shaped configuration for seating a spinous process therein. Each arm has a proximal camming surface and is capable of rotation with respect to the body. An actuator assembly is disposed inside the longitudinal passageway and connected to the body. When advanced, the actuator assembly contacts the camming surfaces of the arms to rotate them from an undeployed configuration to a deployed configuration. In the deployed configuration, the distracted adjacent spinous processes are seated in the U-shaped portion of the arms providing sufficient distraction to open the neural foramen to relieve pain. An insertion instrument is provided for implanting the interspinous process spacer. The system is configured for quick implantation through a small percutaneous incision employing minimally invasive techniques.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 60/923,971 entitled “Interspinous spacer” filed onApr. 17, 2007 and U.S. Provisional Patent Application Ser. No.60/923,841 entitled “Spacer insertion instrument” filed on Apr. 16,2007, each of which is hereby incorporated by reference in its entirety.This application is also a continuation-in-part of U.S. patentapplication Ser. No. 11/593,995 entitled “Systems and methods forposterior dynamic stabilization of the spine” filed on Nov. 7, 2006which is a continuation-in-part of U.S. patent application Ser. No.11/582,874 entitled “Minimally invasive tooling for delivery ofinterspinous spacer” filed on Oct. 18, 2006 which is acontinuation-in-part of U.S. patent application Ser. No. 11/314,712entitled “Systems and methods for posterior dynamic stabilization of thespine” filed on Dec. 20, 2005 which is a continuation-in-part of U.S.patent application Ser. No. 11/190,496 entitled “Systems and methods forposterior dynamic stabilization of the spine” filed on Jul. 16, 2005which is a continuation-in-part of U.S. patent application Ser. No.11/079,006 entitled “Systems and methods for posterior dynamicstabilization of the spine” filed on Mar. 10, 2005 which is acontinuation-in-part of U.S. patent application Ser. No. 11/052,002entitled “Systems and methods for posterior dynamic stabilization of thespine” filed on Feb. 4, 2005 which is a continuation-in-part of U.S.patent application Ser. No. 11/006,502 entitled “Systems and methods forposterior dynamic stabilization of the spine” filed on Dec. 6, 2004which is a continuation-in-part of U.S. patent application Ser. No.10/970,843 entitled “Systems and methods for posterior dynamicstabilization of the spine” filed on Oct. 20, 2004, all of which arehereby incorporated by reference in their entireties.

FIELD

The present invention generally relates to medical devices, inparticular, implants for placement between adjacent interspinousprocesses of a patient's spine.

BACKGROUND

With spinal stenosis, the spinal canal narrows and pinches the spinalcord and nerves, causing pain in the back and legs. Typically, with age,a person's ligaments may thicken, intervertebral discs may deteriorateand facet joints may break down-all contributing to the condition of thespine characterized by a narrowing of the spinal canal. Injury,heredity, arthritis, changes in blood flow and other causes may alsocontribute to spinal stenosis.

Doctors have been at the forefront with various treatments of the spineincluding medications, surgical techniques and implantable devices thatalleviate and substantially reduce debilitating pain associated with theback. In one surgical technique, a spacer is implanted between adjacentinterspinous processes of a patient's spine. The implanted spacer opensthe spinal canal, maintains the desired distance between vertebral bodysegments, increases the neural foramen space and as a result, avoidsimpingement of nerves and relieves pain. For suitable candidates, animplantable interspinous spacer may provide significant benefits interms of pain relief.

Any surgery is an ordeal. However, the type of device and how it isimplanted has an impact. For example, one consideration when performingsurgery to implant an interspinous spacer is the size of the incisionthat is required to allow introduction of the device. Small incisionsand minimally invasive techniques are generally preferred as they affectless tissue and result in speedier recovery times. As such, there is aneed for interspinous spacers that work well with surgical techniquesthat are minimally invasive for the patient. The present invention setsforth such a spacer and associated instrumentation.

SUMMARY

According to one aspect of the invention, an implantable spacer forplacement between adjacent interspinous processes in a spinal motionsegment is disclosed. The spacer includes a body defining a longitudinalpassageway and a longitudinal axis. The spacer further includes a firstarm and a second arm connected to the body and capable of rotation withrespect to the body. Each arm has a pair of extensions and configuredfor containing a spinous process therein. Each arm has a proximalcamming surface. The spacer further includes an actuator assemblyconnected to the body. The actuator assembly includes an actuator havinga proximal end and a distal end. The actuator has at least one bearingsurface at the distal end that is configured to engage each cammingsurface. The actuator is connected to the body and configured to moveinside the longitudinal passageway relative to the body to contact eachcamming surface with the at least one bearing surface and thereby movethe arms from an undeployed configuration in which the arms aresubstantially parallel to the longitudinal axis of the body to adeployed configuration in which the arms are substantially perpendicularto the longitudinal axis of the body to contain adjacent spinousprocesses when in the deployed configuration.

According to another aspect of the invention, an insertion instrumentconfigured for delivering a spacer to an interspinous process space of apatient and deploying the spacer from an undeployed configuration to atleast one deployed configuration to relieve pain is disclosed. Thespacer includes a body, at least one arm connected to and movable withrespect to the body and a spacer actuator having a proximal end and adistal end disposed at least partially inside the body. The spaceractuator is configured to move the at least one arm from an undeployedconfiguration to at least one deployed configuration. The insertioninstrument includes a handle assembly, a first assembly connected to thehandle assembly, a second assembly connected to the handle assembly anda third assembly connected to the handle assembly. The first assembly isconfigured to connect to the body of the spacer at the distal end of theinsertion instrument. The first assembly has a first control at thehandle assembly configured to connect and release the body of the spacerand the first assembly. The second assembly is configured to connect tothe proximal end of the actuator of the spacer at the distal end of theinsertion instrument. The second assembly has a second control at thehandle assembly configured to connect and release the actuator and thesecond assembly. The third assembly is configured to move the secondassembly relative to the body of the spacer for arranging the spacerfrom an undeployed configuration to at least one deployed configuration.

According to another aspect of the invention, a method for implanting aspacer between a superior spinous process and an adjacent inferiorspinous process of a patient's spine is disclosed. The method includesthe step of providing a spacer. The spacer includes a body having aproximal end, a distal end, and a longitudinal axis. The spacer alsoincludes a first arm and a second arm connected to the body at thedistal end. The first and second arms are configured to contain thesuperior and inferior spinous processes. The spacer further includes anactuator configured to move the first and second arms from a low-profileundeployed configuration in which the first and second arms extendparallel to longitudinal axis to at least one deployed configuration inwhich the first and second arms are transverse to the longitudinal axis.The method includes the step of inserting the spacer into aninterspinous process space from the posterior side of the patient andmay be inserted through the superspinous ligament while in theundeployed configuration. The method includes the step of arranging thespacer into at least one deployed configuration.

Other advantages will be apparent from the description that follows,including the drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in conjunction with the accompanying drawings. It isemphasized that, according to common practice, the various features ofthe drawings are not to-scale. On the contrary, the dimensions of thevarious features are arbitrarily expanded or reduced for clarity.

FIG. 1 a illustrates a perspective view of a spacer according to thepresent invention.

FIG. 1 b illustrates a side view of a spacer according to the presentinvention.

FIG. 1 c illustrates a top view of a spacer according to the presentinvention.

FIG. 1 d illustrates a cross-sectional view of the spacer of FIG. 1 ctaken along line X according to the present invention.

FIG. 1 e illustrates an end view of a spacer according to the presentinvention.

FIG. 2 a illustrates a perspective view of half of a body of a spaceraccording to the present invention.

FIG. 2 b illustrates a side view of a half of a body of a spaceraccording to the present invention.

FIG. 2 c illustrates a perspective view of another half of a body of aspacer according to the present invention.

FIG. 2 d illustrates a side view of the other half of a body of a spaceraccording to the present invention.

FIG. 3 a illustrates a perspective view of a superior arm of a spaceraccording to the present invention.

FIG. 3 b illustrates a side view of a superior arm of a spacer accordingto the present invention.

FIG. 3 c illustrates a perspective view of an inferior arm of a spaceraccording to the present invention.

FIG. 3 d illustrates a side view of an inferior arm of a spaceraccording to the present invention.

FIG. 4 illustrates a side, semi-transparent view of a spacer in adeployed configuration according to the present invention.

FIG. 5 illustrates a side, semi-transparent view of a spacer in apartially deployed configuration according to the present invention.

FIG. 6 illustrates a side, semi-transparent view of a spacer in adeployed and extended configuration according to the present invention.

FIG. 7 a illustrates a perspective view of an actuator assembly of aspacer according to the present invention.

FIG. 7 b illustrates a side view of an actuator assembly of a spaceraccording to the present invention.

FIG. 8 illustrates a side view of an actuator assembly of a spaceraccording to the present invention.

FIG. 9 a illustrates a perspective view of a spacer according to thepresent invention.

FIG. 9 b illustrates a side view of a spacer according to the presentinvention.

FIG. 9 c illustrates a top view of a spacer according to the presentinvention.

FIG. 9 d illustrates a cross-sectional view of the spacer of FIG. 9 ctaken along line X according to the present invention.

FIG. 9 e illustrates an end view of a spacer according to the presentinvention.

FIG. 10 illustrates a perspective view of a body of a spacer accordingto the present invention.

FIG. 11 a illustrates a perspective view of a superior arm of a spaceraccording to the present invention.

FIG. 11 b illustrates a perspective view of an inferior arm of a spaceraccording to the present invention.

FIG. 12 a illustrates a perspective view of an actuator assembly of aspacer according to the present invention.

FIG. 12 b illustrates a side view of an actuator assembly of a spaceraccording to the present invention.

FIG. 13 a illustrates a perspective view of a spacer insertioninstrument according to the present invention.

FIG. 13 b illustrates a side view of a spacer insertion instrumentaccording to the present invention.

FIG. 13 c illustrates a cross-sectional view of a spacer insertioninstrument according to the present invention.

FIG. 13 d illustrates a perspective view of a clamp shaft of a spacerinsertion instrument according to the present invention.

FIG. 14 a illustrates side view of a spacer insertion instrument injuxtaposition to a spacer according to the present invention.

FIG. 14 b illustrates a top view of a spacer insertion instrument injuxtaposition to a spacer according to the present invention.

FIG. 14 c illustrates a cross-sectional view taken along line F-F ofFIG. 14 a of a spacer insertion instrument in juxtaposition to a spaceraccording to the present invention.

FIG. 14 d illustrates a cross-sectional view taken along line G-G ofFIG. 14 b of a spacer insertion instrument in juxtaposition to a spaceraccording to the present invention.

FIG. 15 a illustrates a side view of a spacer insertion instrumentconnected to a spacer according to the present invention.

FIG. 15 b illustrates a top view of a spacer insertion instrumentconnected to a spacer according to the present invention.

FIG. 15 c illustrates a cross-sectional view taken along line G-G ofFIG. 15 a of a spacer insertion instrument connected to a spaceraccording to the present invention.

FIG. 15 d illustrates a cross-sectional view taken along line F-F of aFIG. 15 b of a spacer insertion instrument connected to a spaceraccording to the present invention.

FIG. 16 a illustrates a side view of a spacer insertion instrumentconnected to a spacer according to the present invention.

FIG. 16 b illustrates a top view of a spacer insertion instrumentconnected to a spacer according to the present invention.

FIG. 16 c illustrates a cross-sectional view taken along line G-G ofFIG. 16 a of a spacer insertion instrument connected to a spaceraccording to the present invention.

FIG. 16 d illustrates a cross-sectional view taken along line F-F ofFIG. 16 b of a spacer insertion instrument connected to a spaceraccording to the present invention.

FIG. 17 a illustrates a side view of a spacer insertion instrumentconnected to a spacer in a partially deployed configuration according tothe present invention.

FIG. 17 b illustrates a top view of a spacer insertion instrumentconnected to a spacer in a partially deployed configuration according tothe present invention.

FIG. 17 c illustrates a cross-sectional view taken along line G-G ofFIG. 17 a of a spacer insertion instrument connected to a spaceraccording to the present invention.

FIG. 17 d illustrates a cross-sectional view taken along line F-F ofFIG. 17 b of a spacer insertion instrument connected to a spaceraccording to the present invention.

FIG. 18 a illustrates a side view of a spacer insertion instrumentconnected to a spacer in a deployed configuration according to thepresent invention.

FIG. 18 b illustrates a top view of a spacer insertion instrumentconnected to a spacer in a deployed configuration according to thepresent invention.

FIG. 18 c illustrates a cross-sectional view taken along line G-G ofFIG. 18 a of a spacer insertion instrument connected to a spacer in adeployed configuration according to the present invention.

FIG. 18 d illustrates a cross-sectional view taken along line F-F ofFIG. 18 b of a spacer insertion instrument connected to a spacer in adeployed configuration according to the present invention.

FIG. 19 illustrates a partial cross-sectional view of a spacer insertioninstrument connected to a spacer in a deployed and extendedconfiguration according to the present invention.

FIG. 20 illustrates a spacer according to the present invention deployedin an interspinous process space between two vertebral bodies and asupraspinous ligament.

DETAILED DESCRIPTION

Before the subject devices, systems and methods are described, it is tobe understood that this invention is not limited to particularembodiments described, as such may, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting, since the scope of the present invention will be limited onlyby the appended claims.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include plural referents unless thecontext clearly dictates otherwise. Thus, for example, reference to “aspinal segment” may include a plurality of such spinal segments andreference to “the screw” includes reference to one or more screws andequivalents thereof known to those skilled in the art, and so forth.

All publications mentioned herein are incorporated herein by referenceto disclose and describe the methods and/or materials in connection withwhich the publications are cited. The publications discussed herein areprovided solely for their disclosure prior to the filing date of thepresent application. Nothing herein is to be construed as an admissionthat the present invention is not entitled to antedate such publicationby virtue of prior invention. Further, the dates of publication providedmay be different from the actual publication dates which may need to beindependently confirmed.

The present invention is described in the accompanying figures and textas understood by a person having ordinary skill in the field of spinalimplants and implant delivery instrumentation.

With reference to FIGS. 1 a-1 e, various views of a spacer 10 accordingto the present invention are shown. The spacer 10 includes a body 12connected to a superior extension member or arm 14, an inferiorextension member or arm 16, and an actuator assembly 18.

Turning now to FIGS. 2 a-2 d, the body 12 will now be described. Thebody 12 is shown to have a clamshell construction with a left body piece20 (shown in FIGS. 2 a and 2 b) joined to a right body piece 22 (shownin FIGS. 2 c and 2 d) to capture arms 14, 16 inside. With the right andleft body pieces 20, 22 joined together, the body 12 is generallycylindrical. It has a cross-sectional size and shape that allows forimplantation between adjacent spinous processes and facilitates deliveryinto a patient through a narrow port or cannula.

The inside of the body 12 defines an arm receiving portion 24 and anactuator assembly receiving portion 26 with features formed in each ofthe left and right body pieces 20, 22 that together define the arm andactuator assembly receiving portions 24, 26. In one variation, the armreceiving portion 24 includes slots 28 that receive pins formed on thearms 14, 16 such that the pins rotate and/or translate inside the slots28. The actuator assembly receiving portion 26 includes a passageway 30.Other features include a tongue 31 a and groove 31 b for mating with theopposite clamshell.

The outside of the body 12 defines a ledge 32 along at least a portionof the periphery. Notches 34 are formed with the ledge 32 at oppositelocations as shown in FIG. 1 c. The notches 34 are configured forpronged attachment to a spacer delivery instrument and, as seen in FIG.1 c, are of different width to assist the clinician in orienting thespacer 10 with respect to the spacer delivery instrument. When joinedtogether, the left and right body pieces 20, 22 define a proximalopening 36 (as seen in FIG. 1 e) and a distal opening 38 (as seen inFIG. 1 a) in the body 12. A longitudinal scallop (of a type shown inFIG. 10 with reference number 78) extending from the proximal end of thespacer to the distal end on either one or both sides of the body andoppositely located, is formed to facilitate placement of the spacer 10between and to conform to the anatomy of adjacent interspinousprocesses.

Turning now to FIGS. 3 a and 3 b, the superior arm 14 is shown and inFIGS. 3 c and 3 d, the inferior arm 16 is shown. The superior andinferior arms 14, 16 include pins 40 for mating with the body 12, inparticular, for mating with the slots 28 of the arm receiving portion24. Each of the superior and inferior arms 14, 16 includes at least onecamming surface 41, 43, respectively, for contact with the actuatorassembly 18. The superior and inferior arms 14, 16 include elongatedsuperior extensions 42 a, 42 b and elongated inferior extensions 44 a,44 b, respectively. Extensions 42 a and 44 a are located on the leftadjacent to the left body piece 20 and extensions 42 b and 44 b arelocated on right adjacent to the right body piece 22. Superiorextensions 42 a, 42 b extend substantially parallel to each other inboth an undeployed configuration and in a fully-deployed configurationas do inferior extensions 44 a, 44 b. Extending between extensions 42 a,42 b is a strut, bridge, bracket or saddle 46 that forms a superiorsubstantially U-shaped configuration together with the extensions 42 a,42 b that is sized and configured to receive a superior spinous process.As seen in FIG. 3 b, the anterior face of the superior extensions 14includes a slight concavity or curvature 45 for conforming to the bonyanatomy of the superior spinous process and or lamina. Also, as seen inFIG. 3 d, the anterior face of the inferior extensions 16 includes aslight convexity or curvature 47 for conforming to the bony anatomy ofthe inferior spinous process and or lamina. Also, extending betweeninferior extensions 44 a, 44 b is a strut, bridge, bracket or saddle 48that forms an inferior substantially U-shaped configuration togetherwith the extensions 44 a, 44 b that is sized and configured to receivean inferior spinous process of a spinal motion segment.

The superior and inferior arms 14, 16 are movably or rotatably connectedto the body 12, for example by hinge means or the like to providerotational movement from an undeployed configuration to a deployedconfiguration that arcs through approximately a 90 degree range or more.The arms 14, 16 are rotationally movable between at least an undeployed,collapsed or folded state (as shown in FIGS. 1 a-1 e) and at least afully deployed state (as shown in FIG. 4). One of many partiallydeployed states through which the arms move between the fully undeployedand fully deployed state is shown in FIG. 5. In the undeployed state,the arm pairs 14, 16 are aligned generally or substantially axially(i.e., axially with the longitudinal axis defined by the body 12 or tothe translation path into the interspinous space of the patient) toprovide a minimal lateral or radial profile. The longitudinal axis X ofthe body is shown in FIG. 1 c. In the deployed state, the arm pairs 14,16 are positioned such that the U-shaped saddles are in a plane or havea U-shaped projection in a plane that is generally or substantiallytransverse to the longitudinal axis X defined by the body 12 or to thecollapsed position or to the translation path into the interspinousspace of the patient. The arms 14, 16 may also be linearly moveable ortranslatable within the plane from a first deployed state to and from asecond deployed state characterized by an additional extension of atleast one of the arms 14, 16 along the direction of the arrows as shownin FIG. 6. More specifically, the arms 14, 16 can be extended in thegeneral vertical direction along an axis substantially parallel to thespine wherein the arms 14, 16 are extended away from each other and awayfrom the body 12 as denoted by the arrows in FIG. 6. This featureadvantageously allows for the most minimally invasive configuration forthe spacer without compromising the ability to seat and contain thespinous processes in between levels where the process anatomy in suchthat the interspinous process space increases in the anterior directionor without compromising the ability of the spacer to provide adequatedistraction. The arms 14, 16 are connected to the body 12 and/or to eachother in a manner that enables them to be moved simultaneously orindependently of each other, as well as in a manner that providespassive deployment and/or vertical extension or, alternatively, activeor actuated deployment and/or vertical extension.

Turning now to FIGS. 7 a and 7 b, the actuator assembly 18 will now bedescribed. The actuator assembly 18 includes an actuator 48 connected toa shaft 50. The actuator 48 includes a distal end 54 and a proximal end56 and at least two bearing surfaces 58. The bearing surfaces 58 angletowards each other from the proximal end 54 to the distal end 56. Theshaft 50 has a substantially reduced cross-sectional area and includes aneck 60 for connection with a spacer insertion instrument. The actuatorassembly is at least partially disposed inside the body and isconfigured for sliding engagement with respect to the body. The actuator48 includes a slot 61 for receiving an actuator pin 52 seen in FIG. 1 dthat is connected to the body. The actuator 48, with the pin 52 passedthrough the slot 61, is connected to the body in sliding engagement. Thedistal end of the actuator shaft is further configured to engage thesuperior and inferior arms 14, 16 such that forward translation of theactuator relative to the body effects deployment of the arms into atleast one deployed configuration. The at least one deployedconfiguration can be selectively locked into position via the actuatorpin 52 riding inside the slot in the actuator shaft and engaging severalfingers 75 forming one or more constrictions along the slot path. Theconstrictions are configured to lock the pin 52 keeping it fixed in atleast one desired deployed configuration in a friction fit engagement.Four sets of fingers 75 grouped in two sets of two oppositely locatedsets of fingers 75 are shown in FIG. 7 b and are configured such thatthe pin 52 is capable of entering two locked locations between the setsof fingers 75. Typically, a first locked location locks the arms in adeployed configuration and the second locked location locks the arms inan extended-deployed location wherein the pin 52 is resident between twooppositely located sets of fingers when in the at least one lockedlocation. The fingers 75 flex to corral the pin in place.

Another variation of the actuator 48 is shown in FIG. 8. The actuator 48includes an actuator 48 connected to a shaft 50. The actuator assemblyincludes a distal end 54 and a proximal end 56 and at least two bearingsurfaces 58. The bearing surfaces 58 angle towards each other from theproximal end 54 to the distal end 56. The shaft 50 has a substantiallyreduced cross-sectional area and includes a neck 60 for connection witha spacer insertion instrument. The actuator includes several fingers 75forming one or more constrictions along the slot 61 path. Theconstrictions are configured to lock the pin 52 keeping it fixed in atleast one desired deployed configuration in a friction fit engagement.One set of fingers 75 are shown in FIG. 8 and are configured such thatthe pin 52 is pressed in the fingers when in one deployed configuration.

With reference to FIGS. 9 a-9 e, various views of another variation of aspacer 10 according to the present invention are shown wherein likereference numbers are used to describe like parts. The spacer 10includes a body 12, a superior extension member or arm 14, an inferiorextension member or arm 16, and an actuator assembly 18.

Turning now to FIG. 10, the body 12 will now be described. The body 12is shown to have a one-piece construction; however, the body 12 may beconfigured into a clamshell with two mating pieces joined together asdescribed above. The body 12 has a cross-sectional size and shape thatallows for implantation between adjacent spinous processes andfacilitates delivery into a patient through a narrow port or cannula.

The inside of the body 12 defines an arm receiving portion 24 and anactuator assembly receiving portion 26 with features formed therein thattogether define the arm and actuator assembly receiving portions 24, 26.In one variation, the arm receiving portion 24 includes slots 28 thatreceive one or more pins to capture the arms 14, 16 such that the armscan hinge about the pin. As shown in FIG. 10, the slots 28 are formed inflange-like extensions of the body. The actuator assembly receivingportion 26 includes a passageway 30 that conforms to the shape of theactuator.

Still referencing FIG. 10, the outside of the body 12 defines a ledge 32along at least a portion of the periphery. Notches 34 (also shown inFIG. 9 e) are formed with the ledge 32 at opposite locations. Thenotches 34 are configured for pronged attachment to a spacer deliveryinstrument such that a portion of the spacer delivery instrumentsecurely connects with the body. The body 12 defines a proximal opening36 and a distal opening 38. A longitudinal scallop 78 extending from theproximal end of the spacer to the distal end on either one or both sidesand oppositely located, is formed to facilitate placement of the spacer10 between and to conform to the anatomy of adjacent interspinousprocesses. The longitudinal scallops 78 are also shown in FIGS. 9 a and9 e.

Turning now to FIGS. 11 a and 11 b, there are shown figures of thesuperior arm 14 and the inferior arm 16, respectively. The superior andinferior arms 14, 16 include apertures 39 for receiving a pin for pinnedconnection and rotation with respect to the body 12. Each of thesuperior and inferior arms 14, 16 includes at least one camming surface41, 43, respectively, for contact with the actuator assembly 18. Thesuperior and inferior arms 14, 16 include elongated superior extensions42 a, 42 b and elongated inferior extensions 44 a, 44 b, respectively.Extensions 42 a and 44 a are located on one side of the body andextensions 42 b and 44 b are located on the other side of the body.Superior extensions 42 a, 42 b extend substantially parallel to eachother in both an undeployed configuration and in a deployedconfiguration as do inferior extensions 44 a, 44 b. Extending betweenextensions 42 a, 42 b is a strut, bridge, bracket or saddle 46 thatforms a superior substantially U-shaped configuration together with theextensions 42 a, 42 b that is sized and configured to receive and seator contain at least a portion a superior spinous process. As seen inFIGS. 9 b and 11 a, the anterior deployed face of the superiorextensions 14 includes a slight concavity 45 for conforming to the bonyanatomy of the superior spinous process and or lamina. Also, as seen inFIGS. 9 b and 11 b, the anterior deployed face of the inferiorextensions 16 includes a slight convexity 47 for conforming to the bonyanatomy of the inferior spinous process and or lamina. Extending betweeninferior extensions 44 a, 44 b is a strut, bridge, bracket or saddle 48that forms an inferior substantially U-shaped configuration togetherwith the extensions 44 a, 44 b that is sized and configured to receiveand seat at least a portion of an inferior spinous process of a spinalmotion segment.

The superior and inferior arms 14, 16 are movably or rotatably connectedto the body 12, for example by a pin or hinge means or the like toprovide rotational movement to and from an undeployed configuration to adeployed configuration that arcs through approximately a 90 degree rangeor more. The arms 14, 16 are rotationally movable between at least anundeployed, collapsed or folded state (as shown in FIGS. 9 a-9 e) and atleast a fully deployed state (as shown in FIGS. 4 and 6). A partiallydeployed state through which the arms move between the undeployed anddeployed state is shown in FIG. 5. In the undeployed state, the armpairs 14, 16 are aligned generally or substantially axially (i.e.,axially with the longitudinal axis defined by the body 12 or to thetranslation path into the interspinous space of the patient) to providea minimal lateral or radial profile. The longitudinal axis X of the bodyis shown in FIG. 9 c. In the deployed state, the arm pairs 14, 16 arepositioned in a plane generally or substantially transverse to thecollapsed position (i.e., in a plane transverse to the longitudinal axisX defined by the body 12 or to the translation path into theinterspinous space of the patient). The arms 14, 16 are connected to thebody 12 and/or to each other in a manner that enables them to be movedsimultaneously or independently of each other, as well as in a mannerthat provides passive deployment and/or vertical extension or,alternatively, active or actuated deployment and/or vertical extension.

Turning now to FIGS. 12 a and 12 b, the actuator assembly 18 will now bedescribed. The actuator assembly 18 includes an actuator 48 connected toa shaft 50. The actuator 48 includes a distal end 54 and a proximal end56 and at least two bearing surfaces 58. The bearing surfaces 58 angleaway from each other from the proximal end 54 to the distal end 56.Furthermore, the bearing surfaces are displaced laterally from eachother. The shaft 50 has a substantially reduced cross-sectional areaforming a neck or receiving portion 60 for connection with a spacerinsertion instrument. The actuator assembly 18 is at least partiallydisposed inside the body and is configured for sliding engagement withrespect to the body. The actuator 48 includes a slot 61 for receiving anactuator pin 52 seen in FIGS. 9 b and 9 d that is connected to the body.The actuator 48, with the pin 52 passed through the slot 61, isconnected to the body in sliding engagement. The distal end 54 of theactuator 48 is further configured to engage the superior and inferiorarms 14, 16 such that forward translation of the actuator relative tothe body 12 effects deployment of the arms 14, 16 into at least onedeployed configuration. The at least one deployed configuration can beselectively locked into position via the actuator pin 52 riding insidethe slot in the actuator shaft and engaging several fingers 75 formingone or more constrictions along the slot path. The constrictions areconfigured to lock the pin 52 keeping it and the deployed arms fixed inat least one desired deployed configuration in a friction fitengagement. One set of fingers 75 is shown in FIG. 12 b which isconfigured such that the pin 52 is resident between the fingers when inone deployed configuration.

General assembly of the spacers 10 discussed above will now bedescribed. The arms 14, 16 are disposed in the arm receiving portion 24of one body piece. The other of the left or right body piece 20, 22 issecurely connected/welded to the one body piece thereby capturing thearms 14, 16 inside the arm receiving portion 24 such that the arms 14,16 are capable of at least rotational movement with respect to the body12 and in one variation, capable of rotational movement and translationwith respect to the body 12. In the variation in which the body 12 ismade of one piece, the arms 14, 16 are movably connected to the body 12with a pin. The actuator assembly 18 is inserted into the passageway 30of the body 12 and a pin 52 is passed through the body 12 and into theslot 61 of the actuator 48 securing the actuator assembly 18 to the body12 such that the actuator 48 is allowed to slide with respect to thebody 12.

To deliver and deploy the spacer 10 within the patient, the spacer 10 isreleasably attached to a delivery instrument at the proximal end of thespacer 10 via notches 34. The delivery instrument will now be describedin greater detail.

Turning now to FIGS. 13 a-13 c, there is shown an insertion instrument100 according to the present invention. The insertion instrument 100includes a first subassembly 102, a second subassembly 104 and a thirdsubassembly 105 connected to a handle assembly 106.

The first subassembly 102 is configured to releasably clamp to the body12 of the spacer 10 at a distal end 108 of the insertion instrument.Still referencing FIGS. 13 a-13 c, the first subassembly 102 includes afirst clamp shaft 110 and a first outer shaft 112 configured forrelative motion with respect to one another via a first control 114located at the handle assembly 106. With particular reference to FIG. 13c, the first control 114 is threaded to the first outer shaft 112 suchthat rotation of the first control 114 moves the first outer shaft 112along the longitudinal axis 116 of the insertion instrument 100. Reverserotation of the first control 114 reverses the direction of translationof the first outer shaft 112. The first clamp shaft 110 is shown in FIG.13 d. The first clamp shaft 110 is a cannulated shaft fixed to thehandle assembly 106 and configured to be received inside the cannulatedfirst outer shaft 112. The first clamp shaft 110 includes two oppositelylocated, outwardly splayed prongs 118 that are permitted to flexinwardly and return to their outwardly splayed normal position as shownin FIG. 13 d when released. The prongs 118 are configured to be clampedinto the notches 34 formed in the spacer body 12 to clamp onto andsecurely hold the spacer 10 to the insertion instrument 100. As thefirst outer shaft 112 is translated distally in sliding motion withrespect to the first clamp shaft 110 by rotating the first control 114in one direction, the first outer shaft 112 is configured to advanceover the outwardly splayed prongs 118 and deflect them inwardly to clampinto a properly oriented, juxataposed spacer body 12. When the firstouter shaft 112 is translated proximally with respect to the first clampshaft 110 by rotating the first control in an opposite direction, thefirst outer shaft 112 is configured to uncover the prongs 118 allowingthem to flex outwardly to their normal outwardly splayed configurationto release a spacer 10 to which it is connected.

The second subassembly 104 is configured to releasably clamp to theactuator 48 of the spacer 10 at the distal end 108 of the insertioninstrument 100. The second subassembly 104 includes a second clamp shaft120 and a second outer shaft 122 configured for relative motion withrespect to one another via a second control 124 located at the handleassembly 106. The second control 124 is threaded to the second outershaft 122 such that rotation of the second control 124 moves the secondouter shaft 122 along the longitudinal axis 116 of the insertioninstrument 100. Reverse rotation of the second control 124 reverses thedirection of translation of the second outer shaft 122. The second clampshaft 120 is shown in FIG. 13 c and is similar to the first clamp shaft110 except that it is positioned approximately 90 degrees with respectto the first clamp shaft 110. The second clamp shaft 120 is a connectedto the third subassembly 105 and configured to be received inside thecannulated second outer shaft 122. Both the second clamp shaft 120 andthe second outer shaft 122 are located concentrically inside the firstclamp shaft 110. The second subassembly 104 is located concentricallyinside the first subassembly 102. The second clamp shaft 120 includestwo oppositely located, outwardly splayed prongs 126 that are permittedto flex inwardly and return to their outwardly splayed normal position.The prongs 126 are configured to be clamped to the actuator 48 of thespacer 10, and in particular, to the proximal end 56 of the actuator 48at the neck receiving portion 60 of the actuator shaft 50. Any suitableinterface may be formed for connecting to the actuator 48. As the secondouter shaft 122 is translated distally with respect to the second clampshaft 120 by rotating the second control 124 in one direction, thesecond outer shaft 112 is configured to advance over the outwardlysplayed prongs 126 and deflect them inwardly to connect to the actuator48 of a juxataposed spacer 10. When the second outer shaft 122 istranslated proximally with respect to the second clamp shaft 120 byrotating the second control 124 in an opposite direction, the secondouter shaft 122 is configured to uncover the prongs 126 allowing them toflex outwardly to their normal outwardly splayed configuration torelease the actuator 48 of the spacer 10 to which it is connected.

The third subassembly 105 is configured to translate the entire secondsubassembly 104 with respect to the handle assembly 106 (or, in anothervariation, with respect to the first subassembly 102) to therebytranslate the actuator 48 of a spacer 10 with respect to the body 12 ofthe spacer to arrange the spacer to and from deployed and undeployedconfigurations. The third subassembly 105 includes a proximally locatedthird control 128 configured in the form of a removable drive handlethreaded to the second assembly 104 and configured for effectingrelative motion of the second assembly 104 with respect to the handleassembly 106 wherein rotation of the drive handle 128 moves the secondassembly 104 along the longitudinal axis 116 of the insertion instrument100. Reverse rotation of the drive handle 128 reverses the direction oftranslation of the second assembly 104. Because the second assembly 104is connected to the actuator 48 of the spacer 10 such longitudinaltranslation effects translation of the actuator 48 with respect to thebody 12 of the spacer 10. In one variation, the third assembly 105further includes a fourth control 130 for adjusting the position of thesecond assembly 104 relative to the handle assembly 106 such thatdifferently-sized spacers are easily connectable to the insertioninstrument at the distal end. For example, as shown in FIG. 13 b, asetting of large L on the fourth control 130 positions the secondassembly 104 proximally with respect to the handle assembly 106 suchthat a spacer with a longitudinally longer body 12 may be easilyaccepted and connected to the insertion instrument 100 at the distal end108. A setting of small S on the fourth control 130 positions the secondassembly 104 distally with respect to the handle assembly 106 such thata spacer with a longitudinally shorter body 12 may be easily acceptedand connected to the insertion instrument 100 at the distal end 108. Thefourth control 130 may also be employed simultaneously or independentlyof the third control 128 to arrange the spacer to and from deployed andundeployed configurations.

Other features of the insertion instrument 100 include a lock 132configured to lock the first and second subassemblies 102, 104 intoposition to prevent accidental release of the spacer body 12 or spaceractuator 12. A direction indicator 134 is provided on the instrument 100for orientating the instrument 100 with respect to the patient anatomy.In one variation, for example, the direction indicator 134 indicates acephalad orientation. Various depth markings 136 are also provided aswell as connection arrows for lining up the spacer with respect to theinstrument.

Turning now to FIGS. 14 a-14 d, the operation of the spacer 10 andinsertion instrument 100 will now be discussed. In operation, the fourthcontrol 130 is adjusted for the size of spacer 10 to be connected to theinsertion instrument 100. If a longitudinally large spacer 10 is to beconnected, the fourth control 130 is set to large. If a longitudinallysmall spacer 10 is to be connected, the fourth control 130 is set tosmall. This selection positions the distal end of the second assembly104 proximally or distally with respect to the distal end 108 of theinstrument 10 for attachment to the actuator 48. The spacer 10 is thenpositioned proximate to the distal end 108 of the insertion instrument100. The spacer 10 is provided or otherwise placed in its undeployedstate next to the distal end 108 of the instrument. Initially, theprongs 118, 126 are not engaged as shown in FIGS. 14 a-14 d.

Turning now to FIGS. 15 a-15 d, the first control 114 is activated atthe handle of the insertion instrument 100 such that the firstsubassembly 102 is connected to the body 12 of the spacer 10. The firstcontrol 114 is rotated in one direction to advance the first outer shaft112 over the first clamp shaft 110 deflecting the prongs 118 inwardlyinto the notches 34 on the body of the spacer 12 to secure the spacerbody 12 to the instrument as shown clearly in FIG. 15 c. FIG. 15 d showsthat the prongs 126 of the second subassembly 104 are not connected tothe actuator 48.

Turning now to FIGS. 16 a-16 d, the second control 124 is activated atthe handle of the insertion instrument such that the second subassemblyis connected to the actuator 48 of the spacer 10. The second control 124is rotated in one direction to advance the second outer shaft 122 overthe second clamp shaft 120 deflecting the prongs 126 inwardly to clamponto the proximal end 56 of the actuator shaft 50 to secure the actuator48 to the instrument 100 as shown clearly in FIG. 16 d. Althoughdescribed such that the first subassembly 102 is first connected to thebody 12, the instrument 100 may be employed such that the secondsubassembly 104 is connected first to the actuator and then the firstsubassembly 102 is connected to the body. With both the first and secondsubassemblies 102, 104 connected to the spacer 10, the lock 132 ispushed to lock the first and second subassemblies 102, 104 in place toprevent accidental detachment.

To deliver and deploy the spacer 10 within the patient, the spacer 10 isreleasably attached to a delivery instrument 100 at the proximal end ofthe spacer 10 as described. A small midline or lateral-to-midlineincision is made in the patient for minimally-invasive percutaneousdelivery. In one variation, the supraspinous ligament is splitlongitudinally along the direction of the tissue fibers to create anopening for the instrument. Dilators may be further employed to createthe opening. In the undeployed state with the arms 14, 16 in a closedorientation and attached to a delivery instrument, the spacer 10 isinserted into a port or cannula, if one is employed, which has beenoperatively positioned in an interspinous space within a patient's backand the spacer is passed through the cannula to the interspinous spacebetween two adjacent vertebral bodies. The spacer 10 is advanced beyondthe end of the cannula or, alternatively, the cannula is pulledproximately to uncover the spacer 10 connected to the instrument 100.Once in position, the third control 128 and/or fourth control 130 isrotated to begin the deployment of at least one of the superior arm 14and inferior arm 16 or both simultaneously. FIGS. 17 a-17 d illustratethe superior arm 14 and the inferior arm 16 in a partially deployedposition with the arms 14, 16 rotated away from the longitudinal axis116 and the second subassembly 104 advanced distally with respect to thebody of the spacer 12. Distal advancement of the second subassembly 104which is connected to the actuator 48, in turn, distally advances theactuator 48 whose bearing surfaces 58 contact the superior and inferiorcamming surfaces 41, 43 pushing the superior and inferior arms 14, 16into rotation about the pins 40. The position of the arms 14, 16 inFIGS. 17 a-17 d may be considered to be one of many partially deployedconfigurations that are possible and from which the deployment of thearms 14, 16 is reversible with opposite rotation of the third and/orfourth controls 128, 130.

Turning to FIGS. 18 a-18 d, there is shown an insertion instrument 100connected to a spacer 10 in a first deployed configuration in which thearms 14, 16 are approximately 90 degrees perpendicular to longitudinalaxis 116 or perpendicular the initial undeployed configuration.Continued rotation of third and fourth controls 128, 130 moves thesecond subassembly 104 further distally with respect to the body 12 ofthe spacer 10 pushing the bearing surfaces 58 further against thesuperior and inferior camming surfaces 41, 43. While in the firstdeployed configuration, the clinician can observe with fluoroscopy thepositioning of the spacer 10 inside the patient and then choose toreposition the spacer if desired. Repositioning of the spacer mayinvolve undeploying the arms 14, 16 rotating them into any one of themany undeployed configurations. The spacer may then be re-deployed intothe desired location. This process can be repeated as necessary untilthe clinician has achieved the desired positioning of the spacer in thepatient.

Even further advancement of the second subassembly 104 from the firstdeployed configuration results in the spacer assuming a second deployedconfiguration shown in FIG. 19. The second deployed configuration is anextended configuration in which the superior and inferior arms 14, 16extend transversely with respect to the longitudinal axis 116 outwardlyin the direction of the arrows in FIG. 19. Such extension is guided bythe length and shape of the slots 28 in which the arms 14, 16 move. Oncedeployed, the superior arm 14 seats the superior spinous process and theinferior arm 16 seats the adjacent inferior spinous process. Suchextension may also provide some distraction of the vertebral bodies. Asseen in this deployed configuration shown in FIG. 19, the actuator pin52 is seated between the fingers 75 and locked therein.

Following deployment, the lock 132 is released to permit rotation of thefirst and second controls 114, 124 which are rotated in the oppositedirection to release the body 12 and the actuator 48 from the instrument100, respectively. The insertion instrument 100, thus released from thespacer, is removed from the patient leaving the spacer 10 implanted inthe interspinous process space as shown in FIG. 20. In FIG. 20, thespacer 10 is shown with the superior arm 14 seating the superior spinousprocess 138 of a first vertebral body 142 and the inferior arm 16seating the inferior spinous process 140 of an adjacent second vertebralbody 144 providing sufficient distraction to open the neural foramen 146to relieve pain. As mentioned above, the shape of the superior arm 14 issuch that a superior concavity or curvature 45 is provided to conform tothe widening of the superior spinous process 138 in an anteriordirection toward the superior lamina 148 going in the anteriordirection. In general, the superior arm 14 is shaped to conform toanatomy in the location in which it is seated. Likewise, as mentionedabove, the shape of the inferior arm 16 is such that an inferiorconvexity or curvature 47 is provided to conform to the widening of theinferior spinous process 140 in an anterior direction toward theinferior lamina 150. The supraspinous ligament 152 is also shown in FIG.20.

Any of the spacers disclosed herein are configured for implantationemploying minimally invasive techniques including through a smallpercutaneous incision and may or may not be through the supraspinousligament. Implantation through the supraspinous ligament involvesselective dissection of the supraspinous ligament in which the fibers ofthe ligament are separated or spread apart from each other in a mannerto maintain as much of the ligament intact as possible. This approachavoids crosswise dissection or cutting of the ligament and therebyreduces the healing time and minimizes the amount of instability to theaffected spinal segment. While this approach is ideally suited to beperformed through a posterior or midline incision, the approach may alsobe performed through one or more incisions made laterally of the spinewith or without affect to the supraspinous ligament. Of course, thespacer may also be implanted in a lateral approach that circumvents thesupraspinous ligament altogether.

Other variations and features of the various mechanical spacers arecovered by the present invention. For example, a spacer may include onlya single arm which is configured to receive either the superior spinousprocess or the inferior spinous process. The surface of the spacer bodyopposite the side of the single arm may be contoured or otherwiseconfigured to engage the opposing spinous process wherein the spacer issized to be securely positioned in the interspinous space and providethe desired distraction of the spinous processes defining such space.The additional extension of the arm(s) subsequent to their initialdeployment in order to seat or to effect the desired distraction betweenthe vertebrae may be accomplished by expanding the body portion of thedevice instead of or in addition to extending the individual extensionmembers 14, 16. In another variation, the spacer is configured such thatarms are bifurcated side-to-side, instead of top-to-bottom forindependent lateral deployment. For example in such a variation, thespacer includes a left arm and a right arm, instead of a superior armand an inferior arm. The right arm includes extensions 42 a and 44 a andthe left arm includes extensions 42 b and 44 b wherein extensions 42 aand 44 b are deployed independently of extension 42 b, 44 b on the otherside of the spacer. This variation allows for the spacer to be insertedin the same manner as described above and one arm is deployed on oneside of the both the superior and inferior spinous processes and thesecond arm is subsequently deployed on the other side of both thesuperior and inferior spinous processes.

The extension arms of the subject device may be configured to beselectively movable subsequent to implantation, either to a fixedposition prior to closure of the access site or otherwise enabled orallowed to move in response to normal spinal motion exerted on thedevice after deployment. The deployment angles of the extension arms mayrange from less than 90 degrees (relative to the longitudinal axisdefined by the device body) or may extend beyond 90 degrees. Eachextension member may be rotationally movable within a range that isdifferent from that of the other extension members. Additionally, theindividual superior and/or inferior extensions 42 a, 42 b, 44 a, 44 bmay be movable in any direction relative to the strut or bridgeextending between an arm pair or relative to the device body in order toprovide shock absorption and/or function as a motion limiter, or serveas a lateral adjustment particularly during lateral bending and axialrotation of the spine. The manner of attachment or affixation of theextensions to the arms may be selected so as to provide movement of theextensions that is passive or active or both. In one variation, thesaddle or distance between extensions 42 a and 42 b or between 44 a and44 b can be made wider to assist in seating the spinous process and thennarrowed to secure the spinous process positioned between extensions 42a and 42 b or between 44 a and 44 b.

The preceding merely illustrates the principles of the invention. Itwill be appreciated that those skilled in the art will be able to devisevarious arrangements which, although not explicitly described or shownherein, embody the principles of the invention and are included withinits spirit and scope. Furthermore, all examples and conditional languagerecited herein are principally intended to aid the reader inunderstanding the principles of the invention and the conceptscontributed by the inventors to furthering the art, and are to beconstrued as being without limitation to such specifically recitedexamples and conditions. Moreover, all statements herein recitingprinciples, aspects, and embodiments of the invention as well asspecific examples thereof, are intended to encompass both structural andfunctional equivalents thereof. Additionally, it is intended that suchequivalents include both currently known equivalents and equivalentsdeveloped in the future, i.e., any elements developed that perform thesame function, regardless of structure. The scope of the presentinvention, therefore, is not intended to be limited to the exemplaryembodiments shown and described herein. Rather, the scope and spirit ofpresent invention is embodied by the appended claims.

1. An implantable spacer for placement between adjacent interspinousprocesses in a spinal motion segment comprising: a body defining alongitudinal passageway and a longitudinal axis; a first arm and asecond arm connected to the body and capable of rotation with respect tothe body; each arm having a pair of extensions spaced apart from oneanother to define an opening between the extensions, the opening beingconfigured to receive a spinous process; each arm having a proximalcamming surface; an actuator assembly connected to the body; theactuator assembly comprising an actuator having a proximal end and adistal end; the actuator having at least one bearing surface at thedistal end configured to engage each camming surface; the actuator isconnected to the body and configured to move inside the longitudinalpassageway relative to the body to contact each camming surface with theat least one bearing surface and thereby move the arms from anundeployed configuration in which the arms are substantially parallel tothe longitudinal axis of the body to a deployed configuration in whichthe arms are substantially perpendicular to the longitudinal axis of thebody to contain adjacent spinous processes in each arm when in thedeployed configuration.
 2. The spacer of claim 1 wherein the arms areconfigured to rotate with respect to the body in moving from anundeployed configuration to a deployed configuration.
 3. The spacer ofclaim 1 wherein the arms are configured to rotate with respect to thebody about a single axis in moving from an undeployed configuration to adeployed configuration.
 4. The spacer of claim 1 wherein each arm isconfigured to rotate with respect to the body about separate axes. 5.The spacer of claim 1 wherein the arms are configured to rotate withrespect to the body in moving from an undeployed configuration to afirst deployed configuration and then translate with respect to the bodyin moving from the first deployed configuration to a second deployedconfiguration.
 6. The spacer of claim 5 wherein the rotation isapproximate 90 degrees from the undeployed configuration to the firstdeployed configuration.
 7. The spacer of claim 5 wherein each arm isconfigured to rotate outwardly into a planar space that is substantiallytransverse to the longitudinal axis; and each arm is configured totranslate in said plane away from the longitudinal axis in moving fromthe first deployed configuration to a second deployed configuration. 8.The spacer of claim 1 wherein the actuator includes two bearing surfacesthat converge towards the distal end of the actuator.
 9. The spacer ofclaim 1 wherein the actuator includes two bearing surfaces that divergetowards the distal end of the actuator.
 10. The spacer of claim 1wherein the proximal end of the actuator is configured for attachment toan instrument for moving the actuator with respect to the body.
 11. Thespacer of claim 1 wherein the first arm is configured to contain asuperior spinous process and the second arm is configured to contain aninferior spinous process.
 12. The spacer of claim 1 wherein the firstarm is configured to contain one side of the superior and inferiorspinous processes and the second arm is configured to contain the otherside of the superior and inferior spinous processes.
 13. The spacer ofclaim 1 wherein the body includes at least one longitudinal scallopextending along at least a portion of the body; the scallop isconfigured to provide a lower profile for the spacer for insertionbetween adjacent interspinous processes along a posterior midlineapproach while in the undeployed configuration relative to the at leastone deployed configuration.
 14. The spacer of claim 1 wherein each ofthe extensions of the first arm is a first elongate member, the firstelongate members are configured to be positioned on opposite sides of afirst spinous process when the first spinous process is positioned inand extends posteriorly from the opening of the first arm; and each ofthe extensions of the second arm is a second elongate member, the secondelongate members are configured to be positioned on opposite sides of asecond spinous process when the second spinous process is positioned inand extends posteriorly from the opening of the second arm.
 15. Thespacer of claim 1 wherein the body is positioned relative to the firstarm and the second arm such that the longitudinal axis extends in aposterior-anterior direction when a first spinous process is positionedin the opening between the extensions of the first arm and when a secondspinous process is positioned in the opening between the extensions ofthe second arm.
 16. The spacer of claim 1 wherein terminal ends of theextensions of the first arm are spaced apart from one another such thatthe terminal ends are positioned on opposite lateral sides of a superiorspinous process positioned in the opening between the extensions of thefirst arm.
 17. An implantable spacer for placement between adjacentinterspinous processes in a spinal motion segment comprising: a bodydefining a longitudinal passageway and a longitudinal axis; a first armand a second arm connected to the body and capable of rotation withrespect to the body; each arm having a pair of extensions and configuredfor containing a spinous process therein; each arm having a proximalcamming surface; an actuator assembly connected to the body; theactuator assembly comprising an actuator having a proximal end and adistal end; the actuator having at least one bearing surface at thedistal end configured to engage each camming surface; the actuator isconnected to the body and configured to move inside the longitudinalpassageway relative to the body to contact each camming surface with theat least one bearing surface and thereby move the arms from anundeployed configuration in which the arms are substantially parallel tothe longitudinal axis of the body to a deployed configuration in whichthe arms are substantially perpendicular to the longitudinal axis of thebody to contain adjacent spinous processes in each arm when in thedeployed configuration, wherein the actuator includes an elongate slotand the actuator is connected to the body with a pin passed through theslot and connected to the body such that the actuator is configured tomove longitudinally with respect to the body.
 18. The spacer of claim 17wherein the elongate slot includes at least one constriction configuredto lock the pin with respect to the actuator when the arms arepositioned in at least one deployed configuration.
 19. An implantablespacer for placement between adjacent interspinous processes in a spinalmotion segment, comprising: a body having a proximal portion, a distalportion and a posterior-anterior dimension between the proximal anddistal portions; a first arm having a pair of first extensions, a firstcross-member between the first extensions, and a first proximal cammingsurface, wherein the first extensions are spaced apart from one anotherto define a first opening between the first extensions, the firstopening being configured to receive a first spinous process; a secondarm having a pair of second extensions, a second cross-member betweenthe second extensions, and a second proximal camming surface, whereinthe second extensions are spaced apart from one another to define asecond opening between the second extensions, the second opening beingconfigured to receive a second spinous process; a hinge assemblyrotatably coupling the first and second arms to the distal portion ofthe body, wherein the hinge assembly has at least a first pin extendingtransverse to the posterior-anterior dimension to define a firstrotation axis about which the first arm can rotate; and an actuatorassembly coupled to the body to move along the posterior-anteriordimension, the actuator assembly having an actuator including a proximalend, a distal end, a first bearing surface at the distal end, and asecond bearing surface at the distal end, wherein the first bearingsurface is configured to contact the first camming surface of the firstarm and the second bearing surface is configured to contact the secondcamming surface of the second arm as the actuator moves distally therebycausing the first arm to rotate about the first rotation axis from anundeployed configuration to a deployed configuration.
 20. The spacer ofclaim 19 wherein the first and second pairs of extensions are configuredto extend distally at least substantially parallel to theposterior-anterior dimension in the undeployed configuration and rotateproximally to be at least substantially perpendicular to theposterior-anterior dimension in the deployed configuration.
 21. Thespacer of claim 19 wherein the first and second bearing surfaces of theactuator converge towards the distal end.
 22. The spacer of claim 19wherein the second arm is configured to rotate about the first axis. 23.The spacer of claim 19 wherein the hinge assembly further comprises asecond pin extending transverse to the posterior-anterior dimension todefine a second rotation axis spaced apart from the first rotation axis,and wherein the actuator is configured to cause the first arm to rotateabout the first rotation axis and the second arm to rotate about thesecond rotation axis from an undeployed configuration to a deployedconfiguration as the actuator moves distally.
 24. The spacer of claim 23wherein the actuator is configured to rotate the first and second armsat least substantially concurrently.
 25. The spacer of claim 19 whereineach of the first extensions is an elongate member, the elongate membersof the first arm are configured to be positioned on opposing lateralsides of a first spinous process when the first spinous process extendsthrough and posteriorly from the first opening of the first arm.
 26. Animplantable interspinous spacer, comprising: a body defining alongitudinal passageway and a longitudinal axis; a first arm coupled tothe body and rotatable relative to the body, the first arm including apair of first extension members spaced apart to define a first openingconfigured to receive a superior spinous process such that the superiorspinous process extends in a posterior-anterior direction through thefirst opening when the first extension members are positioned onopposing laterals sides of the superior spinous process; a second armcoupled to the body and rotatable relative to the body, the second armincluding a pair of second extension members spaced apart to define asecond opening configured to receive an inferior spinous process suchthat the inferior spinous process extends in the posterior-anteriordirection through the second opening when the second extension membersare positioned on opposing laterals sides of the inferior spinousprocess; and an actuator assembly connected to the body, the actuatorassembly comprising an actuator having a proximal end and a distal end,the actuator having at least one bearing surface at the distal endconfigured to engage each camming surface, the actuator being connectedto the body and configured to move inside the longitudinal passagewayrelative to the body to contact each camming surface with the at leastone bearing surface to move the first and second arms from an undeployedconfiguration in which the arms are substantially parallel to thelongitudinal axis of the body to a deployed configuration in which thefirst and second arms are substantially perpendicular to thelongitudinal axis of the body.
 27. The spacer of claim 26 wherein aportion of the first arm that defines the first opening is sustantiallyU-shaped and a portion of the second arm that defines the second openingis sustantially U-shaped.
 28. The spacer of claim 26 wherein the body ispositioned relative to the first arm and the second arm such that thelongitudinal axis extends in the posterior-anterior direction when thesuperior spinous process is positioned in the first opening and theinferior spinous process is positioned in the second opening.
 29. Thespacer of claim 26 wherein terminal ends of the first extension membersare spaced apart from one another such that the terminal ends arepositioned on opposing lateral sides of the superior spinous processwhen the superior spinous process is positioned in the first opening.